Neuroprotective effects of repeated transient global ischemia and of kynurenine adminsitration induced by four-vessel occlusions on hippocampal CA1 neurons.

The hippocampal CA1 subfield is a brain region that is particularly sensitive to hypoxia. Although this subfield is selectively vulnerable to ischemic injuries manifested in delayed neuronal death (DND), the mechanism leading to neuronal degeneration is not fully understood. Burda recently reported that a second pathophysiological stress, applied within a suitable time, offers an opportunity for salvaging neurons in the CA1 region against DND (Neurochem. Res., 30: 1397-1405, 2005). In our study, NeuN immunohistochemistry was applied to detect survival CA1 neurons, while Fluoro-Jade B staining was used to evaluate the number of injured neurons after interventions resulting in transient global ischemia. Four groups of animals were used: 1: intact controls; 2: sham controls (2 vertebral arteries coagulated (2VAC), but 2 carotids sham-operated); 3: 2VAC + 2 carotids occluded (2CA) for 10 min; 4: 2VAC + 2CA (10 min) + 2 days later, a repeated 2CA (5 min). In group 3 (2VAC + 2CA (10 min)), marked cell destruction was found in the CA1 subfield: only 36.4% of the CA1 neurons survived. However, in group 4 (5-min second ischemic insult), the proportion of surviving cells in the CA1 region was 59.3%. There was no significant difference in CA1 cell loss between groups 1 and 2. Our findings suggest that the second ischemic stress, 2 days after the first ischemia induced by 2VAC + 2CA can be efficient in the prevention of DND. Neuroprotective effect was also found in four-vessel occlusion models after kynurenine (i.v.) administration

A hamis vád

INST: L_08

The mechanism of action and role of hydrogen sulfide in the control of vascular tone

Our knowledge about hydrogen sulfide (H2S) significantly changed over the last two decades. Today it is considered as not only a toxic gas but also as a gasotransmitter with diverse roles in different physiological and pathophysiological processes. H2S has pleiotropic effects and its possible mechanisms of action involve (1) a reversible protein sulfhydration which can alter the function of the modified proteins similar to nitrosylation or phosphorylation; (2) direct antioxidant effects and (3) interaction with metalloproteins. Its effects on the human cardiovascular system are especially important due to the high prevalence of hypertension and myocardial infarction. The exact molecular targets that affect the vascular tone include the KATP channel, the endothelial nitric oxide synthase, the phosphodiesterase of the vascular smooth muscle cell and the cytochrome c oxidase among others and the combination of all these effects lead to the final result on the vascular tone. The relative role of each effect depends immensely on the used concentration and also on the used donor molecules but several other factors and experimental conditions could alter the final effect. The aim of the current review is to give a comprehensive summary of the current understanding on the mechanism of action and role of H2S in the regulation of vascular tone and to outline the obstacles that hinder the better understanding of its effects

H2S preconditioning of human adipose tissue-derived stem cells increases their efficacy in an in vitro model of cell therapy for simulated ischemia

Aims: A major limitation of cell-based therapies for ischemia – reperfusion injury is the excessive loss of adminis- tered cells. We investigated whether H 2 S can improve the survival and ef fi cacy of therapeutic cells in an in vitro model of cell-based therapy for simulated ischemia. Main methods: H9c2 rat cardiomyoblasts were exposed to oxygen – glucose deprivation and NaHS (3 – 30 μ M) pretreated human adipose tissue derived stem cells (hASCs) were added after reoxygenization. Viability of both cell lines was assessed with fl ow cytometry after 24 h. The effects of H 2 S on antioxidant defense, prolifera- tion, AKT and ERK1/2 phosphorylation and mitochondrial activity were analyzed in hASCs. Proliferation was evaluated using propargylglycine, an inhibitor of endogenous H 2 S synthesis. Key fi ndings: NaHS pretreatment decreased the ratio of necrotic therapeutic cells by 41.8% in case of 3 μ M NaHS and by 34.3% with 30 μ M NaHS. The ratio of necrotic postischemic cardiomyocytes decreased by 35%, but only with the use of 3 μ M NaHS. Antioxidant defense mechanisms and ERK-phosphorylation were enhanced after 3 μ M NaHS treatment while AKT-phosphorylation was suppressed. NaHS dose-dependently increased the prolif- eration of hASCs while pretreatment with propargylglycine decreased it. Signi fi cance: NaHS pretreatment can increase the survival of therapeutically used human adipose tissue-derived stemcells viaincreased antioxidant defense andimproves the postischemic cardiac derived cells' survival aswell. Proliferation ofhuman adiposetissue-derivedstemcells is enhanced by H 2 S.The underlying mechanisms involve enhanced ERK-phosphorylation and decreased AKT-phosphorylation. Pretreatment with NaHS may represent a simple pharmacological step that may enhance the ef fi cacy of cell-based therapies

Oxaloacetate decreases the infarct size and attenuates the reduction in evoked responses after photothrombotic focal ischemia in the rat cortex

A traumatic brain injury or a focal brain lesion is followed by acute excitotoxicity caused by the presence of abnormally high glutamate (Glu) levels in the cerebrospinal and interstitial fluids. It has recently been demonstrated that this excess Glu in the brain can be eliminated into the blood following the intravenous administration of oxaloacetate (OxAc), which, by scavenging the blood Glu, induces an enhanced and neuroprotective brain-to-blood Glu efflux. In this study, we subjected rats to a photothrombotic lesion and treated them after the illumination with a single 30-min-long administration of OxAc (1.2 mg/100 g, i.v.). Following induction of the lesion, we measured the infarct size and the amplitudes of the somatosensory evoked potentials (SEPs) as recorded from the skull surface. The photothrombotic lesion resulted in appreciably decreased amplitudes of the evoked potentials, but OxAc administration significantly attenuated this reduction, and also the infarct size assessed histologically. We suggest that the neuroprotective effects of OxAc are due to its blood Glu-scavenging activity, which, by increasing the brain-to-blood Glu efflux, reduces the excess Glu responsible for the anatomical and functional correlates of the ischemia, as evaluated by electrophysiological evoked potential (EP) measurements

Hippocampal (CA1) activities in Wistar rats from different vendors. Fundamental differences in acute ischemia

Two-vessel occlusion, a frequently used model of global cerebral ischemia. in rats, results in a dysfunction predominantly within the CA1 field of the hippocampus; it induces many processes with different time-scales. However, the great divergence in the results of the studies reported in the literature suggests valuable differences in response to hypoperfus ion-induced ischemia among the laboratory rats used in these studies. In the present work, the acute effects of two-carotid occlusion-induced global ischemia (2VO)on the CA3 stimulation-evoked population spike activity in the CA1 region of Wistar rats from different suppliers (Charles-River and Harlan) were compared. In the acute electrophysiological experiments, the hippocampal CA1 responses revealed that the Charles-River rats immediately compensated the 2VO much better than did the Harlan rats. However, 3 days later, no difference could be observed between the CA1 activities of these rats. The presented data show that the Wistar rats from different vendors represent an important source of variability in the results of acute experiments on the hippocampal ischemia. These observations draw attention to the importance of the careful choice of the laboratory rats (both strains and breeds) used in such experiments